topic Re: Verification formulas ANSI/AISC 360-10 in Robot Structural Analysis Forum

Verification formulas ANSI/AISC 360-10

Anonymous — Sun, 14 Jan 2018 13:45:32 GMT

Hello,

Could anyone help me with this?

I am struggling with the design of some members according to ANSI/AISC 360-10 because the calc. note says something about LRFD G2-1 equation but when I read G2-1 equation, this indicates something different.

Also I am getting HUGE sections in some members. I got that an IPE600 for a beam is not strength enough due to this Vry/fi*Vny + frvy,mx/0.6*fi*Fyn < 1 First term is ok but i couldnt find the second one in the code. I think frvy,mx is shear stress for torsion. See captures below. I attached the model as well.

Please help me.

Thanks

Cesar

Re: Verification formulas ANSI/AISC 360-10

mustafahesenow — Sun, 14 Jan 2018 13:50:21 GMT

Hi @Anonymous

This huge shear came because of spike torsion Diagram .

As you can see that this beam supporting the stair case beams and the connection between the stair beam and this beam assumed as rigid connection .

As you know also the I beam section is weak to resist the torsion .

All what you can do is to reduce the Mx by this 2 proposals .

1- The Deck slab will resist the torsion and wont allow the beam to rotate and this is valid for your case.

2-make release of stair beam on this connection so the force will transfer to the beam only vertical shear no Mx.

Re: Verification formulas ANSI/AISC 360-10

Anonymous — Sun, 14 Jan 2018 14:02:26 GMT

Yes, you are right @mustafahesenow

Sorry for the question but if I choose the option 1- The Deck slab will resist the torsion and wont allow the beam to rotate and this is valid for your case. I understand that you propose to ignore torsion in that member. What could I do to get a correct section for that beam? if I ignore the torsion in RSA, is there any option to do that?

Always appreciate your support my friend!

Re: Verification formulas ANSI/AISC 360-10

mustafahesenow — Sun, 14 Jan 2018 14:10:47 GMT

Hi @Anonymous

Yes the is look at attached picture.

Re: Verification formulas ANSI/AISC 360-10

Anonymous — Sun, 14 Jan 2018 14:21:30 GMT

My friend you saved my life.

You rock!

Big massive thank you @mustafahesenow

Re: Verification formulas ANSI/AISC 360-10

mustafahesenow — Sun, 14 Jan 2018 14:22:41 GMT

Hi @Anonymous

You are very welcome Cesar.

Re: Verification formulas ANSI/AISC 360-10

Artur.Kosakowski — Mon, 15 Jan 2018 08:53:31 GMT

Hi @Anonymous

I just wanted to point your attention to the 'correct' use of the functionality @mustafahesenow indicated (thank you for your priceless help for this forum). It is mostly intended for the situation when you have small torsion (or any other internal force type) and it its influence of the section capacity is negligible. If this is not the case ignoring it may not be the best idea and perhaps yup should find out why it is high when it is supposed to be small first. Perhaps using the Rx - Rx partial release with small stiffness value will be worth considering?

Re: Verification formulas ANSI/AISC 360-10

Anonymous — Mon, 15 Jan 2018 13:21:42 GMT

Hi @Artur.Kosakowski

What do you mean with "Rx-Rx partial release with small stiffness value"?

Thanks in advance

Re: Verification formulas ANSI/AISC 360-10

Artur.Kosakowski — Mon, 15 Jan 2018 13:27:35 GMT

Hi @Anonymous

What do you mean with "Rx-Rx partial release with small stiffness value"?

I meant a release like this one:

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Re: Verification formulas ANSI/AISC 360-10

Anonymous — Wed, 17 Jan 2018 11:25:22 GMT

Hi @Artur.Kosakowski

I didn't see your answer before.

Sorry for say it but it didn't work 😞 I used rx-rx partial releases exactly as in your picture in the last post.
That doesn't reduce torsion and consequently shear due to torsion.

Re: Verification formulas ANSI/AISC 360-10

Artur.Kosakowski — Wed, 17 Jan 2018 11:31:05 GMT

Hi @Anonymous

Could you attach the model and indicate a sample beam to look at?

Re: Verification formulas ANSI/AISC 360-10

Anonymous — Wed, 17 Jan 2018 16:12:57 GMT

Hi @Artur.Kosakowski

For example: member 48. Model attached

Without releases

With releases

Re: Verification formulas ANSI/AISC 360-10

mustafahesenow — Thu, 18 Jan 2018 07:51:41 GMT

Hi @Anonymous

If you want to use the release option . you should release the stair beam not the supporting one. in My direction .

Re: Verification formulas ANSI/AISC 360-10

Artur.Kosakowski — Thu, 18 Jan 2018 11:58:14 GMT

Hi @Anonymous

To illustrate what @mustafahesenow (thank you) suggested (as the restrains for rotations are introduced by both stairs and beams along the bar 48 length):

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Re: Verification formulas ANSI/AISC 360-10

Anonymous — Thu, 18 Jan 2018 12:08:54 GMT

Hi @Artur.Kosakowski

Thank you for answer as well as @mustafahesenow

Sorry for asking but what is the difference between "Bar releases" and "Elastic partial releases"?

Re: Verification formulas ANSI/AISC 360-10

Artur.Kosakowski — Thu, 18 Jan 2018 12:15:54 GMT

Hi @Anonymous

Full vs. spring release with rotational stiffness being related to the bar rigidity.

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.